The present invention relates to gyrocompasses and, in particular, to a gyro mounted in a gimbal which is rotatable about an upright axis.
It is known to employ a gyrocompass mounted in an azimuthally rotatable gimbal. These systems typically employ two gimbals outside of the azimuth gimbal which serve to keep the axis of the latter vertical. An error arises when this axis is tilted because of the mixing of the vertical component of the earth's rotation with the horizontal component. Known gyrocompasses employ a gyroscope rotatably mounted in a gyro case with a single degree of freedom about an output axis transverse to the spin axis of the gyroscope. These known gyroscopes rely on the fact that the component of rotation of the earth orthogonal to both the output axis and spin axis of the gyroscope produces a torque about the output axis. This torque can be measured and used to determine the direction of north.
It is also known to use a single gyroscope in both a gyrocompass and directional mode. This known dual function gryoscope is initially aligned with its input axis horizontal to sense the earth's horizontal component of rotation. Subsequently, the input axis is rotated 90 degrees into a vertical position where the gyrscope can determine the direction (azimuthal rotation) of a vehicle supporting the gyroscope.
A disadvantage with some of the foregoing gyroscopic systems is the relative complexity and the need for many gimbals. Therefore, it is an object of the present invention to provide an improved gyrocompass which is simple yet accurate.